Optical telescopes are used in a variety of different applications. These applications primarily are for daytime use under natural lighting conditions and permit the user to discern greatly magnified, but narrow field of view, images as a result of use of the telescope. Typically such telescopes have an eyepiece located near the eye of the user, and the optics of the telescope are selected to cause the focal plane and the optical axis of the telescope to intersect at the location of the eye of the user. Focusing adjustments are provided to individualize this location for most telescopes.
A special application of telescopes is in the form of telescope sights for rifles or other weapons. Such telescope sights typically are mounted on top of the barrel of the rifle or other weapon to permit accurate sighting of the rifle for distant targets. Usually such a telescope sight includes a superimposed fine cross hair which intersects on the optical axis of the telescope for designating the location of the target. Since the optical axis essentially is straight, a telescope sight includes an adjustment which may be made to compensate for the trajectory characteristics of the bullet from the rifle at the particular range or distance at which the target appears. When this adjustment is made, the cross hairs in the telescope theoretically coincide with the termination point of the bullet at the target. For most daytime use, this is sufficient for relatively accurate use of the weapon by a hunter or target shooter once the use of the telescope on the rifle has been mastered.
A significant shortcoming of optical telescope sights, however, exists for use of a rifle equipped with such a telescope sight in poor lighting conditions or at night. The light gathering capabilities of telescopes are limited; and, as a consequence, optical telescopes are practically worthless for any nightime use. To compensate for this disadvantage, point source laser light transmitters have been developed for attachment to a rifle or other weapon in addition to the optical telescope. The laser emits a narrow beam or pencil of light. When this additional laser light source is calibrated to the trajectory of the weapon, it impinges upon or identifies the target of interest.
For use at night, a laser light source operating in the infrared region may be employed. The user of a rifle or other weapon provided with such equipment than must wear some type of night vision image enhancement equipment, such as conventional night vision goggles. With this equipment, the user may utilize the laser light source and the telescope to observe the target. This equipment is highly effective, but the additional laser light source in a separate housing typically is very expensive, because of the additional optics required in conjunction with the laser light source. In addition, the alignment of the weapon now requires three separate systems to be aligned, namely, the optical telescope, the laser source, and the trajectory of the bullet. This in turn, makes the use of the weapon more difficult also.
It is desirable to provide a system which is less expensive than the prior art systems described above, which readily converts any telescope equipped rifle or weapon into a system capable of use at night or day, and which is easy to use and requires minimum training on the part of the operator for accurate utilization.